highlighting intersections
I just followed the method in that link:


you can use add shader in the end but results were not good so I used a mix of 50/50
you can use a light path node with out put of is camera ray to get rid of shadows.





works in eevee too but you should enable ambient occlusion + make the shader show transparency + adjust the color ramp. if adjusting color ramp is hard add a math node with power before it. 



eevee setup